Digital lavalier microphone

Abstract

A lavalier microphone has improved dynamic range. The lavalier microphone incorporates a pair of microphone transducer elements into the same housing or attached housings, with one of the microphone transducer elements being more sensitive to acoustic input than the other. The voltage signals from the respective transducer elements are processed and combined, resulting in a digital output audio signal with improved signal to noise both at lower and higher input acoustic levels.

1 . A microphone with improved dynamic range comprising:
 a first microphone transducer element having a first sensitivity to acoustic pressure input and outputting a first voltage signal in response to acoustic pressure detected by the first microphone transducer element;   a second microphone transducer element having a second sensitivity to acoustic pressure input and outputting a second voltage signal in response to acoustic pressure by the second microphone transducer element; wherein the first sensitivity to acoustic pressure is greater than the second sensitivity to acoustic pressure;   means for amplifying and digitizing the first voltage signal to generate a first digital signal;   means for amplifying and digitizing the second voltage signal to generate a second digital signal;   an internal digital processor, and means for providing DC power to the internal digital processor, the first microphone transducer element, the second microphone transducer element, means for amplifying and digitizing the first voltage signal and means for amplifying and digitizing the second voltage signal;
 wherein the first and second microphone transducer elements, said means for amplifying and digitizing the first voltage signal to generate a first digital signal, said means for amplifying and digitizing the second voltage signal to generate a second digital signal, and the internal digital processor are located within a common housing or attached housings; and further 
 wherein the first and second digital signals can be processed and combined to generate a digital audio output signal with improved signal to noise both at lower and higher input acoustic levels. 
   
     
     
         2 . The microphone with improved dynamic range recited in  claim 1  wherein the first microphone transducer and the second microphone transducer are placed coincidently in order to be exposed to nearly identical acoustic energy. 
     
     
         3 . The microphone with improved dynamic range recited in  claim 2  wherein the first and second microphone transducers are condenser-type transducers and the distance between the center of a diaphragm of the first microphone transducer and the center of a diaphragm of the second microphone transducer is not greater than 1.7 cm. 
     
     
         4 . The microphone with improved dynamic range recited in  claim 1  wherein the microphone is a lavalier microphone, and at least one clip is provided to attach the lavalier microphone to clothing worn by a person or in the hair of a person. 
     
     
         5 . The microphone with improved dynamic range recited in  claim 1  wherein the first digital signal and the second digital signal are input to the internal digital processor and digital data stream representing the first digital signal and the second digital signal is output from the internal digital processor. 
     
     
         6 . The microphone with improved dynamic range recited in  claim 5  wherein the digital data stream out from the internal digital processor is a stereo serial data stream in SPDIF (Sony Philips Digital Interface) format. 
     
     
         7 . The microphone with improved dynamic range recited in  claim 5  further comprising a wire and the stereo serial data stream in SPDIF format is transmitted over the wire from the internal digital signal processor to a wireless transmitter unit. 
     
     
         8 . The microphone with improved dynamic range recited in  claim 1  wherein the internal digital processor is a field programmable gate array. 
     
     
         9 . The microphone with improved dynamic range recited in  claim 1  wherein the microphone has a cord with a conductor that transmits a clock signal (WCLK) superimposed on underlying DC power, a capacitor that functions to separate the clock signal from the underlying DC power transmitted over the conductor to provide the clock signal to the internal digital processor and the underlying DC power to a linear regulator, said linear regulator and said capacitor being located in the housing or attached housings, and said linear regulator providing DC power to the internal digital processor and to the means for amplifying and digitizing the first voltage signal and means for amplifying and digitizing the second voltage signal, and providing biasing voltage to the first microphone transducer element and to the second microphone transducer element. 
     
     
         10 . A method of generating a digital audio output signal with improved signal to noise both at lower and higher input acoustic levels comprising the steps of:
 providing a first microphone transducer element having a first sensitivity to acoustic pressure input;   providing a second microphone transducer element having a second sensitivity to acoustic pressure input, wherein the first sensitivity to acoustic pressure is greater than the second sensitivity to acoustic pressure;   providing a first impedance converter having a first junction field-effect transistor (JFET);   providing a second impedance converter having a second junction field-effect transistor (JFET);   providing a first pre-amplifier and a second pre-amplifier;   providing a first analog to digital converter and a second analog to digital converter;   providing an internal digital processor, wherein the first and second microphone transducer elements, the first and second impedance converters, the first and second pre-amplifiers, the first and second analog-to-digital converters and the internal digital processor are located within a common housing or attached housings;   supplying a biasing voltage to the first microphone transducer element and outputting a first low voltage signal in response to acoustic pressure detected by the first microphone transducer element;   supplying a biasing voltage to the second microphone transducer element outputting a second low voltage signal in response to acoustic pressure by the second microphone transducer element;   inputting the first low voltage signal to the first impedance converter and outputting a first amplified, low impedance voltage signal from the impedance converter;   inputting the second low voltage signal to the second impedance converter and outputting the second amplified, low impedance voltage signal from the impedance converter;   inputting the first amplified, low impedance voltage signal to the first preamplifier and outputting a first amplified voltage signal;   inputting the second amplified, low impedance voltage signal to the second preamplifier and outputting a second amplified voltage signal;   inputting the first amplified voltage signal into the first analog-to-digital converter to generate a first digital signal;   inputting the second amplified voltage signal into the second analog-to-digital converter to generate a second digital signal;   inputting the first digital signal and the second digital signal to the internal digital processor; and   combining the first and second digital signals or signals derived from the first and second digital signals to generate a digital audio output signal with improved signal to noise both at lower and higher input acoustic levels.   
     
     
         11 . The method of  claim 10  wherein the internal digital processor generates a stereo serial data stream in SPDIF (Sony Philips Digital Interface) format from the first and the second digital signals; and the method further comprises transmitting the stereo serial data stream in SPDIF (Sony Philips Digital Interface) format to an external digital processor which in turn is used to generate the digital audio output signal with improved signal to noise both at lower and higher input acoustic levels. 
     
     
         12 . The method of  claim 10  wherein the digital audio output signal is generated within a wireless RF transceiver, an RF receiver, or a mixer recorder. 
     
     
         13 . The method of  claim 10  further comprising the steps providing an external digital processor, transmitting a clock signal over a cord to the internal digital processor, streaming serial data representing the first and second digital signals over the cord from the internal digital processor to the external digital processor, and implementing the combining step on the external digital processor. 
     
     
         14 . The method as recited in  claim 10  further comprises the step of providing a battery and an antenna for wireless communication within the common housing or attached housings and transmitting the digital audio output signal wirelessly over the antenna, wherein the step of combining the first and second digital signals or signals derived from the first and second digital signals to generate a digital audio output signal with improved signal to noise both at lower and higher input acoustic levels is implemented in the internal digital processor. 
     
     
         15 . The method as recited in  claim 10  further comprises the step of providing a battery and an antenna for wireless communication within the common housing or attached housings and transmitting the first and second digital signal in a serial data stream over the antenna, wherein the step of combining the first and second digital signals or signals derived from the first and second digital signals to generate a digital audio output signal with improved signal to noise both at lower and higher input acoustic levels is implemented in an external digital processor. 
     
     
         16 . The method as recited in  claim 10  wherein the first and second microphone transducers are condenser-type transducers. 
     
     
         17 . The method as recited in  claim 10  wherein the internal digital processor is a field programmable gate array. 
     
     
         18 . The method as recited in  claim 10  wherein the first microphone transducer and the second microphone transducer are placed coincidently in order to be exposed to nearly identical acoustic energy. 
     
     
         19 . The method as recited in  claim 10  wherein the first and second microphone transducers are condenser-type transducers and the distance between the center of a diaphragm of the first microphone transducer and the center of a diaphragm of the second microphone transducer is not greater than 1.7 cm. 
     
     
         20 . The method as recited in  claim 10  wherein the common housing or the attached housings are for a lavalier microphone, and method further comprises providing a clip on the lavalier microphone and using the clip to attach the lavalier microphone to clothing worn by a person or in the hair of a person.